
7 

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LIBRARY OF CONGRESS 



029 985 414 



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(Not printed for general distribution.) 



Notes on Mechanical Drawing. 



..* 



Prepared for use at the Massachusetts Institute of Technology. 



BY 



Charles L. Adams. 
Assistant Professor of Drawing. 



Chapters I. and II. 



» 3« 



' - > > 

> 1 i 



Boston, Mass. 
1904. 



|_IBK*KV -t COM 

Two Copies Received 

MAR 10 1904 

Copyright Entry 
CLASS fc. XXc. No. 

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COPY 3l 



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Copyright 1904, by 
Charles L. Adams. 



INTRODUCTION. 

In the construction of mechanical objects, such as buildings, bridges or 
machmes, or in the making of any of the many things ordinarily produced by 'the 
carpenter machinist, sheet metal worker, or stone-cutter, we distinguish two 
pnncpal factors. On the one hand we have the designer, or the person who 
originates, plans, or furnishes the ideas, and on the other hand we have the 
mechanic, who works out these ideas. 

As an example of the relation which must exist between designer and 
mechanic let us suppose the case of a civil engineer having a commission to 
build a subway. We may further suppose that he has all information as to 
route, transportation, etc., and that the preliminary survey and borings have 
been made. The problem which now arises is purely one of thought and the 
imagination. Concentrating thought upon the specifications furnished, and the 
data obtained in the survey and borings, and bringing to bear on these condi- 
tions his knowledge of engineering construction, the engineer in due time 
forms a mental picture of the completed work, and this before any step is 
taken in the direction of actual construction. Indeed, before this step can be 
taken it ,s necessary for the designer to verify his mental picture, to determine 
all measurements, and to decide upon modes of construction. It is evident that 
no one man's powers alone are sufficient to foresee and to retain such a multi- 
plicity of facts. At this point, then, it becomes absolutely necessary for the 
designer to have a means by which he may express the material data and his 
own ideas. Furthermore, it is evident that this means must be such that it is 
intelligible not only to the designer himself but to all persons associated with 
him in the work. 

The means which serves these two ends, of formulating the designer's own 
ideas and of making them intelligible to others, is Mechanical Drawing It 
is, in fact, a language, -the language of engineering and the mechanic arts 



(3) 



Drawing Instruments and Materials. 



CHAPTER I. 

DRAWING INSTRUMENTS AND MATERIALS. 

i. The Outfit. The usual instruments and materials for line drawing are 
shown in Plates I and 2. Several special instruments and materials for brush- 
work are given in Plate 3. 

Having read Articles 2 to 17, first-year Institute students should procure 
the following : — 

1 Set of Instruments. 

2 Drawing-Boards, njx 15^ ins. and 17 x 22I ins. 
2 T-Squares, 15-inch, and 21-inch fixed head. 
Rubber, or Amber triangles as follows: — 

1 45°-45°> 4-inch. 

1 45°-45°, 8 » 

1 3 o°-6o°, 5 " 

1 3o°-6o°, 10 " 

2 Irregular curves (of the shapes shown in Plate 2). 

1 Twelve-inch Architect's Triangular Scale (divided into sixteenths of an inch, 

and scales of -^, -^, A, J, -|, -|, |, 1, ii and 3 ins. to a foot). 
r Pricker. 

3 "Koh-i-noor" Pencils, H, HHH, and HHHHHH. 

1 HHHHHH "Koh-i-noor" Lead (for the compasses). 
1 Dozen Thumb-tacks. 
Drawing-papers (in a strong envelope, 17 x 22^ ins.) as follows: — 

6 Sheets Whatman's Half Imperial, Cold Pressed. 

6 " " " " Hot 

6 " Duplex Detail Paper (cut half imperial size). 

2 " Imperial Tracing cloth " " " 

1 Sheet Rowney's Roll Tracing Paper (cut half imperial size). 
1 Block of White Practice Paper, 11 x 15 ins., 24 sheets. 
1 Faber's Emerald Rubber, 
r Stick India Ink, super-super, half size. 
1 Fine File, or Sand-paper Pad (for sharpening pencils). 
1 Slate Ink Slab, with cover. 
1 Steel Eraser. 



6 Drawing Instruments and Materials. 

i Sand-rubber, Faber's, small. 

i Agate Burnisher. 

i Piece Chamois Skin, size about 10x12 ins. 

1 Fine Oil Stone, 3 inch (for sharpening right-line pens). 

1 Penholder and Pens, — \ doz. each of Gillolt's 303, and D. Leonard & Co. 

' Ball Point, 521 F. 

2 Camel-hair Brushes (of the sizes shown in Plate 3). 

1 Water Glass, and Tumbler (each of the size given in Plate 3). 

1 Medium-sized Sponge. 

1 3-oz. Jar Higgins' Drawing-board Paste. 

If possible the beginner should entrust the purchase of his drawing outfit 
to an experienced draftsman, but if this is impracticable he should deal directly 
with some one of the well-known firms who make a specialty of drafting in- 
struments and supplies, and stand ready to make good any defect found within 
a reasonable time. 



Plate 1 



COMPASSES 



COMPASS PARTS 



rl 



p 




PEN 
LEG 



LENGTHENING 
BAR 



RULING 
PEN 

o ■ 




OPEN FOR 
CLEANING 



SOCKET FOR 

B C AND D 



HAIR SPRING 
DIVIDERS 



K) 



LEAD 



KEY 



R REGULATING 
GUE JOINTS 



BOW SPACERS BOW PENCIL 



BOW PEN 







PRICKER 



<C7 



(7) 



Plate 2. 



DRAWING-BOARD 




TRIANGLES 




0; 



PENCIL 



SQUARE 



s s 
e 8 




READING GLASS 





FLAT SCALE 


//"/"/"/"/ 1 1 1 1 1 1 1 1 1 1 


1 1 1 1 1 1 1 1 1 1 ' 1 1 1 1 1 1 1 l""i*"il 




\\„\>,\>A,A \ \ 


\ \ \ . . v , , \ , , \ , . \\ 



TRIANGULAR SCALE 

in'""i i i i ' i i i i i i i i i i i i i i i i i" 1 " 1 "'"! 

/L.I, I, I ,1 ,1,1.1,1, 1,1,1, 1,1,1,1,1,1,1, I, I, I, III, 1,1, I, III, 1,1, 1,1,1,1, 1,1, 1,1,1,1: 1, I, 1,1,1, /,!..,../ 




INK SLAB 




INDIA INK 



THUMB TACK 



'P*=^ii vStaV w a<^ 



m^wwwj 



STEEL INK ERASER (scalpel) 



unzd 



3 



BURNISHER 



^ 





SANDPAPER PAD 



PORTFOLIO 




IRREGULAR OR FRENCH CURVES 



(9) 



BEAM COMPASS 



•<&Ujf 




PROPORTIONAL DIVIDERS 

a b 



ADJUSTABLE 
T SQUARE 



8" 





Plate 3. 



® » » 



Q-l^^-^-T 



I 



NEST OF 
CABINET SAUCERS 




WATER GLASSES 

Diam. at top 3 ins 



WATER 

COLOR 

IN TUBE 



CHINESE 
WHITE 
IN JAR 





Dram at top 2s ina COLOR IN HALF PAN 



a 




IP 




z 






I\ 




SABLE BRUSH 



ZJt 



< 

D 
h 
O 

< 



CAMEL HAIR BRUSHES 




I A brush at both ends) 



Drawing Instruments and Materials. 13 

2. Instruments. Elaborate sets of instruments are unnecessary and the 
purchase of special instruments may be deferred until they are needed. If the 
student's means will permit he should get the very best instruments, otherwise 






Fig. 1. 



he cannot obtain the best results in his drawing. Moreover, besides obviating 
vexatious incidents attendant upon the use of cheap instruments the best, with 
proper care, will work satisfactorily for years. 



n 



Drawing Instruments and Materials. 



Instruments in cases* are shown in Figs, i and 2. An excellent set, 
Fig. i, includes some one of the higher grade imitations of the Alteneder 
compass, and hair-spring dividers, with genuine Alteneder ruling pens and 




Fig. 2. 

bows. Price (1903) should be in the vicinity of fifteen dollars. If the student 
cares to pay the difference in price, he is strongly advised to have the compass 
which comes with the regular sets changed for one having a hair-spring adjust- 
ment similar to that shown in the next to the last cut, Plate II. 

A minimum priced set (about eight dollars) with which good results can be 
obtained is shown in Fig. 2. Although the pivot-joint instruments and the 
Alteneder style pens are rapidly taking the place of the tongue-joint instruments 
and hinged-nib pen, Fig. 2, the latter are here given as they still appear in 

* A more recent style of case is the folding pocket case with flaps. 



Drawing Instruments and Materials. 



i5 






a 






l— ill 


(| 




(! 


1=3 1 


( 



G 



the dealers' catalogues. The pivot-joint instruments of the same quality as the 
tongue-joint ones are usually supplied at the same price. 

A device, Fig. 3, for 
carrying instruments in 
the pocket is sometimes 
preferred to a case, and 
may be made by the stu- 
dent. It is of chamois 
leather, — cloth-bound on 
the edges if desired, — and 
is fitted with pockets, of 
the same material, for the 
reception of the i n s t r u- 
ments. 

3. The Drawing- 
board. It should be of 
straight-grained, well-sea- 
soned white pine, free 
from sap places and knots 
and neither shellacked nor 
varnished. The cleats 
should be of the same 
wood, tongued and 
grooved, and screwed to 
the board (never glued). The outer edge of each cleat should be perfectly 
straight and the grain of the wood parallel to the edge of the cleat. Ask the 
dealer for a steel straight-edge and with it test the straightness of the working- 
edge of the board. If a straight-edge is not at hand test for straightness by 
this method : (a) Let AB be any edge to be tested. With AB used as a ruler 
draw a very narrow pencil line. Reverse AB, end for end, rule again, and if 
AB is perfect, the two pencil lines will coincide. The metal edge sometimes 
attached to smill drawing-boards is altogether unsatisfactory. To provide for 
the contraction and expansion of the board, due to atmospheric changes, the 
screws should pass through slots in the cleat, having a width equal to the 
diameter of the screw. (See the drawing-board, Plate 2.) With this arrange- 
ment the board is less liable to warp, or split, since, while the heads of the 
screws have sufficient bearing to hold the cleats in place, the slots permit the 
screws to slide when working back and forth with the expansion and contraction 
of the board. 




Fig- 3- 



i6 



Drawing Instruments and Materials. 



4. The T-square. The usual T-square is made of pear wood. A better 
oue has the so-called ebony-lined blade. For greatest accuracy a steel T-square, 
and a special steel edge for the drawing-board are necessary ; but it tends 
to soil the paper and to smear the dry ink lines. In choosing the T-square, see 
that the blade is wholly free from nicks and that the grain is straight and 
parallel to the edge of the blade. Test the straightness of the T-square blade, 
and head either according to (a) Art. 3, or by placing each of these edges 
against a steel straight-edge, held between the eye and the light. The edges 
should be in close contact throughout. 

5. The Triangles. These are made in wood, hard rubber, and amber re- 
spectively. The rubber, and the amber triangles are more accurate than those of 
wood ; the amber is less likely to soil the drawing than the hard rubber, and also 
permits the lines of the drawing to be seen through the triangle, — often a 
decided convenience. In selecting the triangles see that each one is not warped, 
by sighting across its surface. 

To test for "squareness," place the triangle A, Figure 4, on a straight edge, 
and with a very sharp pencil 
draw an accurate line along 
edge a b. If, when the tri- 
angle is reversed (as at A') 
edge a b does not coincide 
with the ruled line the tri- 
angle is not "square." 

To test for the straight- 
ness of the edges proceed 
according to (a) Art. 3, or, Fig. 4. 

holding them between the eye and the light, place two triangles edge to edge, 
or each against a steel straight-edge, and see whether they are in close contact 
throughout. 

6. The Scale. Besides observing whether the scale is perfectly straight 
and free from nicks, see that all edges are thin and sharp, and that the gradua- 
tions are very narrow, clear-cut lines. Blunt edges and muddy graduations 
seriously interfere with accuracy in the laying off of measurements. 

7. Drawing-Papers. The best paper for finished drawing is made by 
J. Whatman. It comes in sheets, has various weights and sizes, and is finished 
in three different styles of surface : hot-pressed, cold-pressed, and rough. The 
hot-pressed has a smooth surface suitable for pencil and fine-line drawings. 




Drawing Instruments and Materials. i 7 

The cold-pressed has a grained, somewhat rough surface which takes well both 
ink line and washes of India ink and color. The rough has a coarsely grained 
surface adapted for bold architectural and water-color rendering. All of these 
surfaces stand erasures well. An excellent paper for office and shop drawing is 
the duplex : it takes well both pencil and ink lines, and stands erasurers, and 
handling. It comes in two tints, cream and drab, is sold in sheets, by the yard, 
or in ten yard rolls, and has widths of 30, 3.6, 42, 56 and 62 inches. Useful for 
practice work and cheaper than the preceding are the German papers, their 
American imitations, and manila paper. 

Standard sizes of drawing papers are as follows : 

Cap, 13x17 inches. Imperial, 22x30 ins. 

Demy, 15x17 ins. Elephant, 23x28 ins. 

Medium, 17x22 ins. Columbia, 23 x 34 ins. 

Royal, 19x24 ins. Altas, 26 x 34 ins. 

Super-Royal, 19x27 ins. Double Elephant, 27 x 40 ins. 

Antiquarian, 21 x 53 ins. 

8. The Pricker is used for laying off measurements and noting points in 
the drawing. A good substitute for the commercial article, shown in Plate 2, 
can easily be made thus : Whittle out of straight-grained, soft wood a handle 
about 3^ ins. long and tapering from |- in. to t 3 ^ in. diameter. Break off the 
eye of a No. 9 sewing needle with a pair of pincers, push the point of the 
needle into the smaller end of the handle, taking care to keep the needle 
accurately in line with the axis of the handle. When it has been pushed in 
say three-fourths of its length, draw it out, reverse it, and force it, broken end 
first, into the hole already made in the handle. The needle should project | in. 

9. The Pencils. The commercial pencil sold for writing purposes is wholly 
unfit for mechanical drawing ; only the best should be procured, and in the 
hexagonal style. The following makes are preferred by draftsmen : Dixon 
(American) L. and C. Hardtmuth, E. Faber, Johann Faber, and A. W. Faber (all 
imported). 

10. The Pencil Sharpener. A small, fine-cut file is often used for sharpen- 
ing pencil and compass leads, but it soon becomes clogged with the lead. A con- 
venient and inexpensive substitute is the sandpaper pad (see Plate 2), a block 
of fine sandpaper fastened to a strip of wood. When a sheet of the pad is 
used, it is removed to expose a fresh one. A piece of fine sand-paper, or emery 
cloth fastened to a strip of wood, say 6 x i\ x ■£$ ins. will do very well. 



1 8 Drawing Instruments and Materials. 

ii. The Thumb-tacks. Tacks costing from five to twenty cents a dozen are 
sufficiently good. Small copper tacks (not iron ones) are sometimes used. The 
shank of the thumb-tack should be slender, the points very sharp and the head 
thin, the upper or curved surface intersecting the lower or plane surface in a 
sharp outline, that it may not catch the edge of the T-square~blade. The shank 
should be so fastened to the head that, when pressed into the drawing-board, 
it will not push through the head into one's thumb. Steel tacks which have the 
points stamped out of the head are good in this respect ; they are also easily 
withdrawn with the finger nail, but the edge of the head is rather thick. 

12. The Rubber Eraser. Select a piece of rubber that is soft and pliable. 
For cleaning inked drawings the sponge rubber is best for large areas ; the 
kneaded, or velvet rubber for cleaning around and between the lines. 

13. The India Ink. The best ink gives a glistening, black line and is satis- 
factory for brush work ; while lines made with cheap inks are apt to look dead, 
tend to smear easily, and are unsuitable for brush work. A stick, half-size, at 
fifty cents, is the cheapest that should be considered. 

14. The Steel Ink Eraser. A surgeon's scalpel is recommended, as the steel 
is far superior to that in ink erasers usually found at the stationers. Length 
should be about 5^ ins., and the shape as shown in Plate 2. 

15. The Burnisher. The cut, Plate 2, shows one of the various styles of 
agate burnishers. The instrument is used after an erasure of ink-lines, to pre- 
pare the paper for the re-inking of lines. 

16. The Brushes. The best brushes for wash drawings are Winsor and 
Newton's Sables. As these in large sizes are expensive, camel-hair brushes 
are frequently used instead. Japanese brushes are inexpensive and excellent. 
All brushes should be tried in water at the time of purchase. When filled 
with water and passed quickly downward, across the edge of the glass, the 
brush should recover to form a sharp point. The snappier the movement 
on the hair the better the brush. 

THE USE AND HANDLING OF THE INSTRUMENTS. 

17. Before speaking of the instruments in detail we may call the reader's 
attention to several general points. On beginning actual drawing the student 
should remember that he is beginning the study of a language, and a practical 
one (see Introduction). He, therefore, should not look upon his work merely as 
a school requirement, or as concerning him only for the time being, but as a 
necessity if he purposes to become a draftsman, an engineer, or an architect. 



Drawing Instruments and Materials. 19 

the use and manipulation of the instruments. 

17. Before speaking of the instruments in detail we wish to call attention 
to several general points. The reader should remember that he is taking up the 
study of a language, and a practical one (see Introduction). In order that he may 
learn the more quickly to use this language effectively, he should imagine that 
the processes and ideas presented in the instruction are in reality his own, — that 
they spring from within himself, — in order that he may always feel, when draw- 
ing, that he is expressing some thought, or idea which is distinctly his own. By 
so doing he learns to think for himself, and in the language of drawing. Fur- 
thermore, he should not look upon his work merely as a school requirement, 
or as concerning him only for the time being, but as absolutely indispensable 
if he purposes to become a draftsman, an engineer, or an architect. If he 
intends to follow other lines, he should know that, as affecting all scientific 
work, mechanical drawing is an effective means for acquiring precision of 
manual execution, of observation, and of thought. 

Regarding the working or practical side of drawing, it should be understood 
that the methods here presented are not the only ones which exist, and that 
draftsmen often differ in their ideas of the way in which a thing should be done. 
The traditions, and the character of the work of a particular office often 
influence the methods of the draftsman. A beginner, however, should take 
pains to carry out instructions literally and in the best of faith, until, having 
learned to work according to one method, he reaches a point where he is com. 
petent to judge of others. 

Concerning one's self, the advantage of workmanlike habits should be kept 
in mind. Avoid lounging on the drawing-table, and like lazy habits. An erect 
position at the drawing-table, and quiet, brisk attention to the work in hand are 
not only suggestive of one's general quality, but are conducive to better results 
in drawing ; while the former is also important from the standpoint of health. 
The care of the instruments, of the drawings, — finished and under way, — and 
of the drawing-papers, demand proper attention. It is worth while also to have 
an eye to the orderly arrangement of things on the drawing-table, and to leave 
everything in. order on stopping work. 

18. Examination of the Outfit. The student should now get together his 
instruments and materials and become familiar with them through comparison 
with Plates 1, 2, and 3. The remarks on these Plates should be noted and 
the names memorized. 



20 



Drawing Instruments and Materials. 




Fig- 5- 



19. The Care of the Instruments and Materials. The instruments should 
be kept clean, free from moisture, and always in good working order. The pens 
should be sharpened properly and should not be allowed to become 
clogged with ink. The joints of the compasses should be regulated to 
work freely, neither loose nor stiff. A trifling quantity of oil may be 
used on the regulating screws of the pens and bow instruments, if these 
do not turn easily. Leads that are too short, and needle-points that 
have become blunted should not be used in the compass, and bow-pencil. 
When the instruments are not in use, the tension of all springs should 
be released ; that is, the bow-instruments, and the blades of the pens 

should be left open (A, Fig. 5). In opening and closing 
the bows, pinch the legs together with the fingers, — so 
that the pressure will be taken off the regulating nut 
(A, Fig. 6), — turn the nut, and then let the leg spring 
gently back against it. When the instruments are not 
to be used for a considerable time, they should be 
rubbed with a slightly oiled rag. 

Regarding materials, a drawing-board is less likely to warp 
when stood on edge, so that the air may circulate about it, than 
when left lying flat. If a drawing-board is re-planed to remove 
dents, it should be planed on both sides, since it is more likely to 
warp if planed only on one side. It is best to keep the T-square 
and triangles hung up, when not in use, away from sunlight and 
heating apparatus. The working-edge of the drawing-board, the 
head of the T-square, and the T-square blade should be tested 
(Arts. 3 and 4) from time to time, and if found inaccurate should be trued. 
Drawing papers should be kept flat. The stick of India ink should be wiped 
perfectly dry after being used, otherwise it will crack, or crumble. Liquid ink 
should be kept covered to prevent thickening and to keep out dust. 

20. Precision and Speed in Drawing. The accuracy with which a drawing 
need be made depends upon the purpose it is to serve. For example, the graph- 
ical solution of problems in certain machine and engineering drawing calls 
for the strictest accuracy. In a construction or working drawing, - — one having 
measurements lettered on it, — it is usually necessary to be only fairly accurate. 
In certain architectural drawing a very free treatment is the most satisfactory. 
At the outset, however, every student, whatever the character of his prospective 



Fig. 6. 



Drawing Instruments and Materials. 



21 



work in drawing, should strive for strict accuracy ; not until he has learned the 
full meaning of precision, and acquired the power to work accordingly, should he 
turn his attention to free methods. ^ 

At the same time the question of speed must be considered. In general, 
as compared with free treatment, precision of execution implies diminished 
speed. It does not follow, however, that in order to obtain precise results it is 
necessary to work slowly ; from the start there should be sustained effort to com- 
bine both accuracy and speed. To accomplish this requires knowledge of 
methods, and judgment in their use. Moreover, it is evident that due care is 
necessary for precision, and brisk execution for speed ; but fussiness must not 
be mistaken for due care, nor mere bustle for speed. The question of speed is 
largely one of the use of wits, in adopting direct and labor-saving methods, rather 
than one of quickness of hand. 

21. The Line of 
Sight in Execution. As 
affecting precision, it is 
important always to 
keep in mind the posi- 
tion of the eye rela- 
tively to all parts of the 
drawing, and to the in- 
strument in use at the 
time. To secure the 
best results, each por- 
tion of the drawing, 
when observed, should 
lie in a plane perpen- 
dicular to the line of 
sight. Thus in viewing 
the drawing-paper, 
Fig. 7, in the vicinity of B, the plane of the paper DEF should be perpendicular 
to the line of sight AB. Therefore, in order to satisfy this condition as fully 
as possible, the draftsman should work standing, that he may easily move about 
so his line of sight will always be perpendicular to the paper for each observed 
portion of the drawing. To the same end, if sitting, he should remember, when 




Fig. 7. 



22 



Drawing Instruments and Materials. 



passing from one part of a drawing to another, to change the position of the 
board. A block to incline the drawing-board is convenient. 

In ruling lines, the draftsman's head 
should move with the ruling-point. If the head 
remains in a fixed position and only the eye 
follows the ruling-point, it is evident that, as 
the point moves away from the eye, the angle 
which the line of sight makes with the paper 
constantly decreases ; at the same time the 
chance of error increases. Also, in ruling, the 
eye should see the line of contact of ruler and 
paper; to meet this condition it is evident 
that the line of sight cannot remain perpen- 
dicular to the paper, but angle BAC, Fig. 7, 
should be kept as small as possible. In laying off measurements from the 
scale, the line of sight should be as nearly perpendicular to the paper as possible 
at the particular division on the scale which is to be laid .off ; that is, angle 




Fig. 8. 




Fig. 9. 



BAC, or BAD, Fig. 8, should be no greater than is necessary to bring into 
view the point of the pricker, or pencil. 



Drawing Instruments and Materials. 23 

For lines longer than, say 12 ins., ruling should be done standing and as 
shown in Fig. 9. The draftsman stands facing the drawing and with the left 
side of the body turned toward it. Leaning over the drawing, the line of sight, 
AC, is directed slightly forward and inward from perpendicular AB to the paper; 
forward, in order to see in advance of the moving point D, and inward, to see dis- 
tinctly the line of contact of the ruler and the paper. If a line to be ruled is a 
long one, the body should face in the direction of the required line, to permit the 
draftsman to walk forward easily in following the hand. This method insures 
greater accuracy in stopping a line at a given point. 

22. Testing. The habit of frequently checking, or testing a drawing is 
the surest way to secure accuracy. In professional practice it is the only safe- 
guard against costly mistakes. 

This subject is fully presented in connection with the exercises. 



Having pointed out the foregoing features of the general subject, we now 
take up details necessary to prepare the way for the first exercise in drawing. 
A 8 c d e r 






23- 



Fig. 10. 
The Sharpening of Pencils and Compass Leads. 



(a) The ruling-point. 



24 



Drawing Instruments and Materials. 



Cut away the wood of the 6 H pencil to expose at least half an inch of the lead 

(A, Fig. 10). 

With the file or sandpaper pad resting on something solid, as the edge of 

the drawing-table, and with the forefinger on the wood where it meets the lead 

(Fig. 1 1), press the lead lightly but firmly against 
the sandpaper, and with a steady back-and- 
forth motion grind opposite sides of the lead to 
form an accurate wedge (see edge view 2? -and 
side view C, Fig. io). Next, holding the pen- 
cil as in Fig. 12, carry it very lightly back and 
forth, and with each separate stroke slightly 
rotate the pencil about its axis in the opposite 
direction to that of the stroke. This rocking 
motion forms the finished point {D and E, 
Fig. 10). It will be noted that, seen sideways, 
the contour of the point is elliptical (E, Fig. 10); 
a cross section of the point gives the form 
shown at ab, E, Fig. 10. The advantage of 
&' Ir ' this point is that, by slightly changing the 

angle of the pencil, when ruling, the draftsman may obtain a succession of 

sharp points. 

Another ruling point sometimes used is formed by first making a conical 

point (E, Fig. 10) and then grinding its opposite sides to form a wedge. 

(b) The measuring-point . For this point, which is often used instead of the 

pricker, to lay off measurements 

from the scale, the pencil is worked 

to a slender and extremely sharp 

conical point (E, Fig. 10). When 

forming this point, carry the lead 

back and forth on the sandpaper, 

meanwhile constantly rotating the 

pencil about its axis. 

It is convenient to sharpen Fig. 12. 

the opposite ends of the same pencil for the ruling and the measuring points. 





Drawing Instruments and Materials 



25 



(c) The sketching-point. This point is used for putting in an occasional 
free-hand line on the mechanical drawing, for sketching in lettering, writing on 
the drawing, etc. It should be conical in form, less slender than F, Fig. 10, and 
only fairly sharp. For this purpose an H, or HH pencil should be used. 

(d) Compass leads. The leads for the compass, and bow-compass should 
be placed in the sockets of these instruments and then sharpened. Let the lead 
extend well beyond the socket of the in- 
strument, that the latter may not come in 
contact with the sandpaper. Form the 
point according to the directions for form- 
ing a ruling-point [a, Art. 23). When sharp- 
ened, the lead should be adjusted in the 
socket as shown in Figs. 13 and 14. It will 
be seen that, when the legs of the compass 
are closed (Fig. 13), — the needle-point 

projecting about § inch 
beyond its socket, — the 
needle should project 
slightly beyond the tip of 
the lead (see the distance 
in Fig. 13). When the 
compass is open (Fig. 14), 
the plane ab of the lead 
should be perpendicular to 
a plane passing through 
the axes c d and e/oi the 
legs. 

Fig. 14. 

24. The Plate, the Size of the Paper, the Border-line, Trimming. 

(a) The subject matter of a drawing or plate is usually circumscribed by a 
ruled border-line, EEEE, Fig. 15. In laying out a drawing, the size and loca- 
tion of the subject matter may be determined with respect to a border-line of 
some given size, or, according to circumstances, the size and arrangement of 
the subject matter may determine the size of the border-line. When a drawing 
is completed and the border-line drawn, the width of the margin, DDDD 
Fig. 15, of the plate should be laid off; lines CCCC, should then be ruled 




26 



Drawing Instruments and Materials. 



through the points of measurement, and the plate trimmed on these lines. 
Therefore, before cutting off paper, AAAA, for a drawing, ascertain the re- 
quired size by adding to the dimensions of the border-line twice the width of 
the margin, plus an allowance of extra paper, BBBB, for thumb tack holes, 

which should fall out- 
side the trimmed 
edge. 

(b) A very 
sharp knife should 
be used for trimming 
drawings. When 
trimmed on a board, 
the drawing should 
be placed in such a 
position that the 
knife will be drawn 
across the grain of 
the wood rather than 
in the direction of 
the grain. If this is 








B 
* 


C 















E 


D 






«B> 












<B> 


c 


E 
«-D-> 








E 
< D> 


C 








E 


D 

1 






o 




* 

B 

. y 


C 






o 



A 

Fig. 15. 



not done, the knife will tend to follow the grain and thus prevent a straight cut. 
In this respect the best cutting surface is thick, smooth cardboard laid on the 
drawing-board. Neither the regular drawing-board nor the T-square should be 
used in trimming drawings, but separate ones should be kept for this purpose. If, 
as a last resort, the drawing-board and the T-square are used, the cutting should 
be done on the back of the board, and along the lower edge of the T-square. 

(c) In using the T-square, the bearing of its head against the drawing- 
board is maintained by placing the hand on the head below the blade (Fig. 7). 
When the blade of the T-square lies along the lower edge of the drawing-board, 
it becomes necessary to shift the hand above the blade in order to keep the head 
in position. This is both inconvenient, and a cause of inaccuracy, and should be 
avoided by placing the paper, when practicable, well above the lower edge of 
the drawing-board (Fig. 17). Never begin work on paper larger than the 
drawing-board ; if the paper projects beyond the board, at once trim it so 
that all edges will lie at least -| in. inside the edges of the board. Smooth 
out the paper flat on the drawing-board. Start the thumb-tacks at right angles 
to the board (A, Fig. 16), so that, when pressed in, their heads will bear evenly 
on the paper (B, Fig. 16). Never use the T-square to drive in thumb-tacks. 



Drawing Instruments and Materials 



27 



When not working on an unfinished 
drawing, keep it covered with a clean 
cloth, or paper. In making carefully 
executed plates, and elaborate draw- 
ings, all parts not in immediate use 
should be kept covered. 

(d) To lay out a border-line : Take 
for example an 8 in. x 12 in. border- 
line with a 1 in. margin. Let A A, 
Fig. 1 7, represent the edges of the paper 
as cut for a drawing. With the aid of 
the T-square, place the edges of the 





A 






II I Avoid b 


1 =1 


; > 1 




















Fig. 16. 



paper approximately parallel to the edges of the drawing-board. Next, as it is 
likely that the edges of the paper are irregular and the sheet not square, draw, 

with T-square and 
triangle, horizontal 
and vertical lines, BB, 
\ in. or less from the 
edge of the paper, 
as an allowance for 
trimming, and thumb- 
tack holes. Perpen- 
dicular to lines BB 
lay off 1 in., the given 
width of the margin. 
Draw lines C C of in- 
definite lengths and 
lay off the width and 
Fl S- I7 " the height of the 

border-line. Complete the border with T-square and triangle. When a strictly 
accurate border is necessary, it should be laid out by geometrical construction. 

(e) Second Method. It is sometimes convenient in laying out a border to 
work from the center of the sheet, in which case proceed as follows : Find 
the center C of the sheet (Fig. 18). Through this point draw AB and DE, 




28 



Drawing Instruments and Materials. 



/ / 




Fig. 19, clear across the paper. On 
AB lay off CF and CG respectively 
equal to half the width of the re- 
quired border-line. On DE lay off 
CH and CK respectively equal to 
one-half the height of the ruled 
border-line. Draw horizontal lines 
through points //and K, and through 
F and G draw vertical lines. An 
objection to this method is the 
erasure of the construction lines, 
which injures the paper for laying 
flat washes and other brush-work. 
Fig. 18. 

25. Drawing Scales. If the meas- 
urements of a drawing are the same as 
those of the object represented, the 
drawing is said to be "full size," and the 
scale commonly used is one of inches 
and sixteenths of an inch. Drawings 
are said to be drawn to a scale when 
they are made, for convenience or from 
necessity, smaller or larger than the 
areas or objects represented. For ex- 
ample, respecting areas, we may have a map of the United States drawn to a 
scale of 1 inch =400 miles ; also, surveyor's plans to scales of 50 ft. to the inch, 
80 ft. to the inch, and so forth. Drawings of'mechanical objects are made half 
size, quarter size or 3 ins. to the foot (written 3 ins. = 1 ft.), eighth size or \\ 
ins. to the foot (1 *- ins. = 1 ft.) etc. Of the various drawing scales manufactured 
we shall speak of but two, the Architect's, divided as stated in the list of 
materials (Art. 1), and the Engineer's, having divisions of 10, 20, 30, 40, 50 and 
60 feet to the inch. 

(a) To read the Engineer s Scale: Take for example, the face of a 12 in. 
scale (Fig. 20), where each inch is divided into 50 parts, indicated by the " 50 " 




Fig. 19. 



. A B 


c 


d e 






imp 


111111111 


llllllll 


llllllll! 


llllllll 


llllllll 


llll|lll||llll|ll 


' 2 4 8 




56 60 ^ 



Fig. 20. 



placed at the middle of the scale (see F). Each of these divisions represents 
1 ft., and the scale is said to be one of 50 ft. to an inch. It will be seen that 



Drawing Instruments and Materials. 



29 



groups [of five divisions, as AB (Fig. 20), and of ten divisions, as DE, are 
denoted by the greater length of the graduations, and that each group of 
twenty ^divisions is indicated by a figure stamped on the scale, as the " 2 " 
opposite C, which is read 20 ft. It will also be noted that inches are not distin- 
guished by number ; if required, these must be found by means of the group 
divisions and numbers. Thus for example, reading from the left-hand end of 
the scale, 1 in. is obtained by taking graduation E (Fig. 20), midway between 
the 4 (= |o of an inch), and the 6 (= fo of an inch). It will be seen, in the 
actual scale, that even inches fall on the numbered graduations, as the 6 ins. on 
the 30, while odd inches fall midway between them ; as the 9 ins. midway 
between the 44 and the 46. 

(b) To read the Architect's Scale: One face of the triangular Architect's 
Scale is divided to read inches, and sixteenths of an inch. On each of the 



Kif »N 

BE F G H j 


y 2 


ii|ii njTT 


1 






1 


r il io s 


I 



L 




c 








3 


A 










1 


1 II II 


MM 


1 1 1 1 1 II 










20 






3 


6 


9 




1 




L 




. 










~ > 



Fig. 21. 

other faces are two scales combined into one. Take for example, the face of 
a 12 in. scale (Fig. 21), divided for scales of \ in. = 1 ft., and 1 in. = 1 ft. It 
will be seen that each scale is denoted by a numeral, or a fraction, stamped 
at the end of the scale, as the "■§■" in space B, and the "1" in space A 
(Fig. 21). Consider first the scale of 1 in. = 1 ft. The space CD (== 1 in.) is 
divided proportionally to a foot rule, except that the lesser divisions of the foot 
rule are omitted in the scale, where the smallest divisions represent half inches. 
To use the scale, read both ways from the zero, opposite C ; inches to the right, 
feet to the left. Each whole foot is distinguished by a numeral (as the " 1 " 
opposite L ), which for this scale is stamped on the concave surface. For the 
scale of \ in. = 1 ft., the space EF (= \ in.) is divided, only here the smallest 
divisions represent inches. To use this scale, read both ways from the zero 
opposite F ; inches to the left, feet to the right. Each whole foot is marked 
by a line, while each second foot is distinguished by a numeral (as the " 2 " 
opposite H). 

To use the scale, apply accurately to the line to be measured, pressing it 
firmly upon the paper to minimize chance of error. To illustrate the reading of 
measurements, let it be supposed that the scale is applied carefully to lines MN 
and OP, Fig. 21. In the former the 3 ft. division is placed at point iVand the 
reading is 3 ft. - 5 in. In the latter, the t ft. division is placed at point O and 
the reading is 1 ft. -7! in. 

• The scale should never be used as a ruler. 



30 



Drawing Instruments and Materials. 



26. Manipulation of T-Square and Triangles, (a) Horizontal lines are usually 
ruled with the aid of the T-Square. Holding the T-Square as shown in Fig. 7, 





Fig. 22. 

press its head firmly against the left-hand cleat of the drawing-board, and the 
blade flat against the paper. Incline the pencil to the right (Fig. 22), and 
slightly away from the T-Square blade (Fig. 23), so that the face of the lead 
will bear against the blade, and the point of the lead will lie in the line of 
contact of the edge of the blade and the paper. Let the fingers rest on the 
T-Square blade (Fig. 22) ; press the pencil firmly but lightly on the paper, 
carry it steadily from left to right, keeping the pressure uniform, and without 
changing the initial position of the pencil. 

(b) Vertical lines are usually ruled with the aid of one of the triangles 
placed against the blade of the T-Square held as for horizontals. With the 
T-Square placed in position, the left hand holding its head firmly against the 
drawing-board, slide the hand from the head of the T-Square along the blade, — 
to keep it in position ; place the triangle against the blade, (Fig. 24), with the 




Fig. 24. 



Drawing Instruments and Materials. 



3i 



right hand, and hold the triangle in position with two fingers of the left hand 
(Fig. 24), thus freeing the right hand to manage the pencil. In ruling, the line of 
sight, AC, Fig. 24, should incline inward and forward from the perpendicular AB to 
the paper, in order that the ruling-point may be kept accurately in the line of con- 
tact of the edge of the triangle and the paper. Move the pencil away from the 
T-square blade rather than towards it. Care should be taken, on beginning a 
drawing, to place the work so that direct light will fall on the working edges of 
the T-square blade and the triangle. For accurate results, all vertical lines through- 


















1 




t. 




hi 



















\ — ' 




Fig. 25. 



Fig. 26. 



out the drawing should be drawn with the same edge of the same triangle, and care 
should be taken that this triangle is not turned over or reversed. 







\ 








/ 






< — 




\b a/ 
^ \ / /~\ 


/' 








00' * 



— 



















r\\ r 




^ \r 






3 












Fig. 27. 



Fig. 28. 



(c) Lines making the angles of 15 , 30 , 45 °, 6o°, or 75 ° with the horizontal 
are ordinarily drawn as shown in Figs. 25-28. 



32 



Drawing Instruments and Materials. 



In drawing a line through a given point, as C, in line AC (Fig. 26), do not fit 
the T-square to the line as at A'C (Fig. 26), and then attempt to place the corner 
of the triangle at the point, as at C, but keep the T-square blade away from the 
line, as at AC, and pass the edge of the triangle through the point. 

(d) For lines parallel or perpendicular to an oblique line, or making the 
angles of 15 , 30 , 45 °, 6o°, or 75 ° with it, we ordinarily use only the triangles. 

To draw a line parallel to a given line : Let it be required to draw through 
point C (Fig. 29) a line parallel to AB. Fit accurately to the given line an edge 




of either triangle, as M, and place against it another triangle, as N. Hold N 
firmly in place with the left hand, L, and slide the triangle M along N to position 
M', with its edge passing through the given point C. Keep M' and N firmly in 
position with the left hand, to free the right hand for drawing the required line, as 
from E through C. 

Positions of the triangles for drawing a perpendicular to an oblique line, or for 
making with it any of the angles stated above, are shown in Fig. 30, which is 
intended for general reference. The solid black represents a fixed triangle ; and 
the dash and dot, a movable triangle set upon the given line. The full line — the 
triangle which guides the pencil — shows either the new position of the movable 
triangle, or the position of a triangle substituted for it (J, K, L and M ). The 
method C, Fig. 30, which uses two movable triangles, is occasionally more con- 
venient, although less direct than the other methods giving the same results. 

(e) The protractor. This instrument, used for laying off angles, is a semi- 
circular disc, or arc — made of metal, horn, cardboard, etc. — divided into degrees, 
half, and quarter degrees. Metal protractors with a vernier attachment read to 
one minute. 



Drawing Instruments and Materials. 



JO 




Fig. 30. 



27. Handling the Compass. Large circles and circular arcs are drawn, ac- 
cording to length of radius, with the compass, the compass with the extension har, 
or the beam-compass. For small circles of, say, t-inch radius or less, the bow- 
compass is used. In drawing circles and circular arcs, the shoulder tip of the 



34 



Drawing Instruments and Materials. 



needle-point (Plate i) should be used, and the lead of the compass should be 
sharpened and adjusted in the socket according to d, Art. 23. 

(#) To describe a circle. First set the compass approximately to the re- 




Fig. 31. 



Fig. 32. 



Fig. 33- 



quired radius, with the legs bent so that each will be perpendicular to the paper 
(Fig. 14). Then set the compass to the exact radius. Now hold the head of 
the compass with the tips of the thumb and the index and middle fingers (Fig. 

31), and place the lead at A, which 
represents a point as near as practi- 
cable to the foot of a perpendicular let 
fall from the inner side of the wrist to 
the paper. The needle-point should 
merely rest on the paper ; do not 
puncture the paper, but give the in- 
strument only enough pressure to keep 
the needle-point from slipping, and to 
obtain the friction necessary to draw 
a very narrow, sharp-cut, and light but 
distinct line. Incline the head of the 
compass slightly forward in the direc- 
tion of its motion, — as indicated by 
the arrows, Figs. 31-33, — and describe the circle with one continuous sweep 
of the lead. The compass should be guided by a combined finger, wrist, and 
arm movement, the head of the instrument meanwhile rolling between the thumb 
and forefinger (Figs. 31-33). 




Fig- 34- 



Fig. 35- 



Drawing Instruments and Materials. 



35 



The need of bending the needle-point leg and of inclining the compass but 
slightly to the paper is shown in Figs. 34 and 35, where A represents an enlarged 
needle-point, B an edge of the paper, and B' its surface. When the needle-point is 
perpendicular to the paper (Fig. 34), if the latter is accidentally punctured, the hole or 
center thus made will have a diameter a' V ' , equal only to the diameter ab of the point. 
If, however, the needle-point is inclined (Fig. 
35), the swinging of the compass is very 
likely to cause the needle-point to ream out 
the puncture to an extent {ab, a'b') which 
prohibits the further use of the center for 
accurate work. Do not carry the lead back 
and forth ; once drawn, let a line stand, — 
improvement should come from practice, and 
not from going over or patching the lines. 
Never use the instrument as shown in Fig. 36. 

(b) The lengthening bar. When the lengthening bar (Fig. 37) is used, 
the compass is likely to spring under pressure ; hence it must be handled lightly. 




Fig. 36. 




Fig. 37- 



Bend the legs to bring them perpendicular to the paper ; incline the instrument 
slightly, in the direction of its motion, and at the beginning and end of the line 
guide the describing leg with a finger of the left hand. 

(e) The beam-compass. This instrument (Plate 3) is practically a compass 
with a separated head (A and B, Plate 3) which slides on a wooden bar. Slight 
corrections of distance between the legs of the compass may be made by means of 
the spring regulated by the nut C. 

28. The Ruling of Curves. (,7) Elliptical and all other curves not circular 
require the use of a curved ruler, one style of which is called the irregular or 



36 



Drawing Instruments and Materials. 



French curve (Plate 2). When the points in a curve have been located, they 
should first be connected by a free-hand line sketched very lightly with a 3H or 
4H pencil having a sharp point. In sketching this line, care should be taken to 
pass it accurately through each of the points located, and at the same time to 
obtain a curve as graceful as possible ; furthermore, the freehand line should be 
drawn directly, since excessive correction tends to obscure, or wholly to obliterate, 
the located points. The free-hand curve having been sketched, the final line, 
usually ruled directly in ink, should be drawn with the French curve as follows : 
Let BCD (Fig. 38) be a series of points connected free-hand as just described. 




Fig. 38. 



The next step will be to find by trial, from among the stock of French curves, 
those having portions which will coincide with or accurately fit the sketched line, 
taken in consecutive sections, each of which should be as long as practicable. In 
order to insure smoothness of curvature in the line as a whole, in ruling each suc- 
ceeding section the French curve must be fitted back some distance on the pre- 
ceding (inked) section. Likewise and for the same reason, in ruling each section, 
the line should stop a little short of the full length of the section. These require- 
ments are illustrated in Fig. 38. Curve A fits section BG of the sketched curve 
BCD, but the ink line is carried only from B to F. Curve A' fits section GK, and 
also fits back on section BG to include portion EF already inked. The ink line is 
carried from F to J; that is, distance JK short of the full length of section 
GK. Curve A" fits back on section GK to H, which includes portion HJ already 
ruled, and forward to point M. The ink line is carried from J to L. 



Drawing Instruments and Materials. 



M 




In ruling- curves, the pen should be held perpendicular to the paper (Fig. 39), so 
that, when carried around sharply curving por- 
tions of the French cu/ve, it may turn easily on 
its point. 

(l>) A template. This is a substitute — 
made by the draftsman — for the French curve, 
and used either as a time-saving device, or when 
the French curve cannot be fitted to the located 
points. It is made of thin sheet metal, wood, 
rubber, or celluloid. If thin wood is used, the 
required curve may be drawn directly on it. In 
the case of rubber or celluloid the curve should 
be traced and then transferred to the rubber by 
pricking through the points (c, Art. 29). The 
template should be roughed out with a pen-knife 
or hand fret-saw, then 'formed with a coarse file, and finished with a fine file. 

29. The Pricker ; Precision in Noting Line Intersections and Scale Measure- 
ment ; Duplicate Drawings. The pricker is used to define line intersections, to 
lay off measurements from the scale, and in duplicating drawings. A fine needle 
should be used, and immediately replaced when the point becomes at all blunted. 
Hold the p'-;<~ u er perpendicular to the paper (Fig. 40) . In the case of intersec- 
tions and scale measurements, do not drive the point 
of the needle through the paper, but make an inden- 
tation which is barely visible. Immediately, when 
an isolated point or one denoting measurement is 
noted, the point should be enclosed in a small free- 
hand circle. 

(a) Line intersections. In noting line intersec- 
tions, the beginner is very likely to be careless. If 



Fig. 39. 




Fig. 40. 




strictly accurate results are specified, 
it is not sufficient merely to glance 
at the intersections ; they must be 
closely scrutinized and noted with the 

greatest precision. To this end we c 

may conceive every line, however 
narrow, to have an imaginary center- 
line. For instance, in Figs. 41 and 
42 the black areas (B) represent the Fig. 41. 

given lines (A) supposed to be mag- 
nified ; the white lines on the black areas represent the imaginary center-lines of 




?8 



Drawing Instruments and Materials. 



the given lines. 



For strict accuracy, we must regard intersections e (A, Figs. 

41, 42) as intersections of the im- 
aginary center-lines of ab and cd, and 
corresponding, to the intersections of 
the white lines (£). To illustrate 
further, let us consider a point of 
tangency, as that of lines ab and cd, 
Fig. 43. Having first determined 
the point g by locating geometrically 
the line ef, in pricking the point with 




Fig. 42. 

the needle we must see in imagina- 
tion the center-lines of ab, cd, and ef, 
as suggested by the white lines on 
the black ground (B). 

(b) Equally important in pre- 
cise drawing is close observation in 
laying off scale measurement. Here, 

. also, we should 




llllllllllllllllllllf 

abcdef 



II II II II II II 

a' b c' d' e' f 



Fig. 44. 



we snouici note the imaginary center-line, in this 
case that of each graduation required to be indicated (see 
a' , //, — f, B, Fig. 44, which represents the graduations of 
actual scale A enlarged). 

(c) Diagrams, maps, and other drawings are some- 
times duplicated as follows : Place the original over a fresh 
sheet of paper. Prick through its essential points, and 



connect the new points in the usual ways. 
The pricker must be held perpendicular to 
the paper. In order that points in the 
duplicate may be readily found, as well as 
to guard against connecting wrong ones, 
each point should be circled freehand, and 
lettered or numbered. 

30. Spacing with the Hair-spring Di- 
viders. The hair-spring dividers and the 
bow-spacers (Plate 1) are used to transfer 
distances, and to space or divide lines into 
equal parts. 

(d\ The general process. Before com- 
mencing to space, ascertain the range (BC, 
Fig. 45) of the hair-spring leg by turning 



8 a c 



the screw E. 



Set the point of the leg at 



Fig 45 • 



Drawing Instruments and Materials. 39 

A midway between B and C. Let it now be required, for example, to divide line 
D'B' (Fig. 46) into 13 equal parts. Take between the points of the dividers — 

moving" the legs by means of the head- 
f 4 . V'TTV' »».\ »» joint — a distance as nearly equal to t l 

— T — o* — I — p... ? — &* — " e — e — « e » ' ° i — 

Z>'5" as can be judged by eye. Start- 
Fig. 46. ing with one leg of the dividers placed 

at D' , step along the given line until 
the 1 3 spaces are laid off. If, in laying off the last, or 1 3th, space, the leg of the 
dividers extends beyond the given line, as distance B' A vii , the assumed distance 
taken in the dividers must be decreased by T * of the excess, B'A V ", determined by 
judgment. If, however, in laying off the 13th space, the leg of the dividers does 
not reach the end of the line, as at C, it is evident that the distance in the dividers 
must be increased by -^ of the deficiency CB' . 

In correcting a distance in the dividers, if the error is a considerable one, the 
leg of the instrument should be moved by means of the head-joint. For a slight 
correction use the hair-spring, which, as already stated, should be set before begin- 
ning to space, so that the leg may be moved in either direction according to 
necessity. 

(b) Refinements in spacing. To divide a line accurately into any considerable 
number of parts requires close observation, careful manipulation of the dividers, 
and strict attention to the following details. As to the instrument, its points 
should be very sharp, of exactly the same length, and, when closed, should come 
together accurately. If the points are blunted, or of unequal length, the defect 
should be remedied on the oil-stone. Until a close approximation to the required 
spacing unit is obtained, the dividers should be stepped parallel to and a little to 
one side of the given line in order not to mar it. In stepping the dividers, care 
should be taken not to spring them, and thus change the distance between the 
points of the instrument, — a result which will follow if the points are thrust into 
the paper. When a close approximation to the required spacing unit has been ob- 
tained, the trial spacing should be transferred to the given line ; but the paper must 
not be punctured or perceptibly indented, since the points of the dividers are very 
likely to slip back into the puncture, or indentation, and thus to frustrate all efforts 
for a satisfactory result. At this 
stage of the spacing, it is not 
sufficient that the points of the 
dividers fall somewhere near the 
given line, or even somewhere 
on this line ; but they must be 
placed on the imaginary center-line of the given line, as suggested by the white 
line on the black ground (B, Fig. 47) — using a reading-glass (Plate 2) if necessary. 




Fig 47- 



40 



Drawing Instruments and Materials. 




Fig. 48. 



To illustrate, in the enlargements C and F (Fig. 47), the points of the divi- 
ders are supposed to fall on opposite edges of the given lines (A and D). It will 
be seen that the distances between the points of the dividers — represented by 
the white lines in C and F, instead of being laid off in one direction, as when 
they fall continuously on the imaginary center-lines (B and E), are laid off in a 
zigzag line. Now, if the points of the dividers happen to fall several times on 
the inner edge of the given line, then several times on the outer edge, next on the 
imaginary center-line, and so forth, there may occur an appreciable accumulated 
error. To minimize chance of error in this particular, let the advancing leg swing 
in alternate directions, as indicated by the lettering and arrows (Figs. 46 and 48). 
In indicating a final spacing, the paper should be 
merely indented, and this not directly, but by going 
over the given line several times, each time with 
just enough pressure to indent the paper visibly 
after the several repetitions. 

(c) Proportional dividers. This instrument 
(Plate 3) is occasionally very convenient in making 
reduced or enlarged copies of drawings, photo- 
graphs, or prints. A required ratio, as between distances ab and cd (Plate 3), is 
obtained by means of the sliding joint A' . 

31. Inking ; the Ruling-pen. A drawing may be inked for each or any of these 
purposes : greater distinctness, finish, or durability. Inking should always be pre- 
ceded by accurate pencil construction, except in the cases of small tangent arcs, 
conventional screw-threads, and parallel lining (cross-hatching) used to denote a 
section of an object, when it should be done without preliminary penciling. India 
ink should be used ; writing inks are wholly unsuitable. For best results it is 
necessary to use the stick ink ground in water. The ready prepared drawing-inks, 
while convenient for rush work in office practice, are not here recommended for 
finished drawing, since they are likely to flow less satisfactorily than the freshly 
ground ink, to be not strictly black, and to attack the paper more quickly. 

(a) To prepare India ink. Fill the ink-slab (Plate 2) with water sufficient 
to overflow the ink-well. Plold the stick of ink vertical, and with a moderate 
pressure give it a rotary motion around the edge of the ink-well. The grinding 
should be continued until the ink is absolutely black, but not thick. This requires 
ordinarily from five to ten minutes, according to the hardness of the ink and the 
amount of water used. As the grinding proceeds, the condition of the ink should 
be ascertained by lines on drawing-paper made with the ruling-pen ; but do not try 
to judge the blackness of the ink until the line is dry. After grinding, the stick 
of ink should be wiped dry to prevent cracking. Keep the ink covered. 



Drawing Instruments and Materials. 



4i 




(b) Ruling. Open the blades of the pen T V" or less, let the ends rest in the 
ink a moment, close the blades, and carefully wipe off all superfluous ink with a rag 
or the chamois leather. If preferred, the common writing-pen, or a quill may be 
dipped in the ink and then passed between the blades of the pen. Always, before 
inking is begun, the pen should be tried — on paper of the kind used in the draw- 
ing — to see that the ink flows freely and that the line is of the right width. Avoid 
the habit of touching the pen to the lips, to cause the ink to flow. If one or two 
trials on the edge of the paper, on the finger, or on the drawing-board — when the 
pen should follow the grain of the wood — will not suffice, either the ink is too 
thick or the pen needs to be cleaned. 

It is best to hold the pen perpendicular to the paper (Fig. 49), or very nearly 

so, with the set-screw turned outward. Thus held, 
the pen will not cover the point to which a line is re- 
quired to be drawn, as is the case when the pen is 
inclined. Carry the pen from left to right steadily, 
rather slowly, and without any rotation about the axis 
of its handle. To satisfy this last condition, the posi- 
tion of the hand relative to the ruler must not 
change ; this is effected by an arm movement from 
shoulder and elbow, without wrist motion. In the 
case of long lines a slight movement of the wrist ap- 
pears to be necessary, but this should not be allowed 
to change the position of the hand relatively to the blade of the T-square or the 
straight-edge. Except in the case of curved shade lines, ruled lines should be of 
uniform width throughout, and wholly free from ragged edges. If the handle of 
the pen is inclined outward — with the object of bringing the point into the line of 
contact of the ruler and the paper — the ruler, especially if made of rubber, is likely 
to attract the ink and thus to blot the paper. Blotting-paper should always be at 
hand in case of accident. Do not set the ink-slab on the drawing-boai'd, or hold 
the pen over the drawing while filling. 

(c) The care of the ruling-pen. The blades of a good drawing-pen are highly 
tempered and therefore brittle ; care should be taken not to break their points by 
screwing the blades too tightly together, or, when filling the pen, by striking 
the points against the ink-well. If a pen works badly, the blades should be 
slightly separated, and examined with a magnifying glass to see whether the points 
are broken, dull, or of unequal length. If the points are dull, this will be indicated 
by a light spot — due to the light reflected by the blunted points — seen when the 
pen is viewed endwise. Every student should learn to sharpen his pen, since in- 
ability to do this may prove to be a serious handicap if he chances in the future 
to be located at a point remote from instrument repair shops. 



Fig. 49. 



42 



Drawing Instruments and Materials. 



(d) To sharpen the ruling-pen. Use a fine oil-stone, and plenty of oil. 
With the blades closed, hold the pen perpendicular to the face of the oil-stone, 
as indicated by views A and D (Fig. 50). While keeping the pen in a plane per- 




Fig. 50. 

pendicular to the surface and parallel to the long edges of the oil-stone, carry the 
pen back and forth, and at the same time rock the pen as indicated by positions 
B and C, Fig. 50. This should bring the blades to an equal length and give them 
points which, for the view of the pen shown in A, Fig. 50, are elliptical in outline. 
Now grind separately the point of each blade as follows : Hold the pen as shown 
at A, Fig. 51, making an angle of about io° or 12 with the surface of the 

stone. Carry the pen back and forth as indi- 
cated by the arrows, and, while so doing, rotate 
it about the axis of its handle. In this rotation 
the right-hand edge of the blade, in passing from 
A to A', gradually approaches the surface of 
the stone. At A' the pen is rotated to corres- 
pond to its initial position at A (see B), and in 
the stroke from B to B' the left-hand edge of 
the blade gradually approaches the stone. The 
pen is again rotated to its initial position at A, 
and the motions are continued. In a cross-sec- 
tion of the point thus made the curved por- 
tion of its outline should be approximately ellip- 
tical. As the work proceeds, the point should 
Fig. 51. be examined from time to time with the reading- 




Drawing Instruments and Materials. 



43 



glass (Plate 2), and the pen should be tested by lines carefully ruled on paper of 
the same kind as is used in the drawing. As a rule, care, patience, and consid- 
erable time are necessary in order to grind a pen properly. 

32. Tracing. For temporary drawings, for transfers, and in planning, trac- 
ing-paper is well-nigh indispensable. Tracings for blue prints and tracings required 
to stand handling, and ink erasure, should be made on tracing-cloth. 

The dull surface of the tracing-cloth is suitable for penciling and inking. 
Washes of India ink and color may be used on the dull surface if applied sparingly ; 
but even then — since water destroys the sizing — the cloth will cockle. If color 
washes are used, inking should be done on the opposite or glazed side. A very 
good substitute for color washes, which is growing in favor, is hard colored crayon ; 
this may be simply rubbed on the dull surface, or, in addition, worked flat with a 
stump. The glazed surface of the cloth is adapted only for inking ; although for 
this work the dull surface appears to be generally preferred. If the cloth does not 
take the ink satisfactorily, it should be thoroughly cleansed by rubbing with soft 
paper, or sprinkled with powdered chalk (scraped from blackboard crayon), which 
should be lightly rubbed into the surface and then dusted off thoroughly. As 
tracing-cloth is very susceptible to moisture — which causes it to stretch — 
it should not be used when permanent accuracy of drawing is required. 

33. Erasure, [a) Pencil-line. Use a soft rubber which is clean 
and pliable. To erase within a small space, the rubber may be shaved 
to a point or to a wedge-shaped edge ; and a card may be used, if nec- 
essary, to protect adjacent lines. For large areas the sponge rubber is 
convenient and time-saving. When efasing near the edges, special care 
must be taken not to crumple the paper or the tracing-cloth ; hold it 
clown firmly with the thumb and finger, and erase between them. 

{b) To remove ink-lines from drawing-paper. In the correction or 

removal of ink-lines or of blots, and in the subsequent redrawing of lines 

after erasure, the work should be so nicely clone that the result will in 

no wise mar the drawing, — a matter requiring care and considerable 

skill. In an erasure, every vestige of ink should be removed. Both 

the steel eraser and sand rubber (rubber ink-eraser) may be used to 

advantage, and the first step toward skilful erasure lies in keeping the 

Fio-. 52. steel eraser very sharp. The scalpel (Plate 2), if a new one, should be 

reground, and afterwards kept to a keen edge by frequent whetting on 

the oil-stone. The form shown in Fig. 52 is recommended. This edge, but 

slightly convex, is best adapted for erasing areas ; while the point, if kept sharp, is 

very satisfactory for minor erasures and cleaning up ragged lines. 



44 



Drawing Instruments and Materials. 



Before beginning to erase a line, note with the finger whether sufficient ink is 
deposited on the paper to give the line appreciable relief. If so, the steel eraser 
should first be used — carried along the line, not crosswise — to remove as much 
of the ink as possible without scraping the paper ; after which the sand-rubber 
should be applied. In using any kind of eraser, the principal thing is not to make 
grooves or ruts in the paper ; hence the eraser should be carried over the paper 
for some distance on all sides of the area to be removed, so that the paper 
may be worn away uniformly. To the same end, in converting a full line into 
dashes, carry the steel eraser back and forth in the direction of the line, not cross- 
wise. To prevent ink from spreading, when redrawing after erasure, the surface 
of the paper should be thoroughly but lightly polished with the burnisher (Plate 
2). Excessive gloss, due to burnishing, may be removed, after the redrawing is 
finished, with the soft rubber. 

Especially useful is the erasing shield — cut out of thin sheet rubber, celluloid, 
bristol-board, or paper — , and used in connection with the rubber eraser. Various 

A B C D 






Fig- 53- 



forms of this device are suggested in Fig. 53, which represents a section of the 
lower end of a locomotive hand-rail stud. Cut A shows a supposed series of mis- 
haps (F, G,J, K, L) to the drawing; B shows the various shields (F 1 , G',J', K' , 
L') used in erasing the accidents; in C we have the drawing after making the 
erasures; and in D the restored lines. The shield M' (B) is used in reducing 
the excess width of the shade lines M (A). The full line lettered E (A, B, C) is 
mistake in inking, since, as the line in the drawing represents an invisible edge of 



Rendering. 45 

the object, it should be expressed by dashes (see E, cut D). The line lettered 
H (A, B, C) represents a visible edge of the object (see H, cut D), and should 
therefore be made a full line. 

(c) To remove ink-lines from tracing-cloth. Slip a piece of cardboard, or the 
triangle, under the cloth for a backing, and erase with either a ruby or emerald rub- 
ber, after having first removed accumulations of ink with the steel-eraser, which 
must not come in contact with the cloth. Before redrawing, apply talc (sold by 
hardware dealers under the name "metal worker's crayon"), and then polish with 
the burnisher. Lines drawn on the glazed surface of the cloth can be much more 
easily removed with the soft rubber than lines drawn on the dull surface ; but in 
neither case should the sand rubber be used, as it will quickly wear a hole through 
the cloth. 



CHAPTER II. 

RENDERING; WORKING METHODS; LETTERING AND DIMENSIONING; STUDY PLATES. 

34. Rendering. This term signifies results wholly dependent upon the 
material used and the manner in which it is applied to the drawing-surface. 
Thus, for example, we have line-drawings in pencil, and in ink ; shaded drawings, 
rendered with pencil, pen and ink, or brush ; finished drawings, sketches, and sug- 
gestions. Various line-renderings or conventions are shown in Fig. 54. Greater 

f Full line * 

For I 

problems <j Dash line . . . . 



1 Q 

[_ Dash and dot line . 

f Visible lines . . EL 

Shade lines . . . E 

Invisible lines . . ^ 



For 
working ^ 
drawings Center-lines . . . 5_ 

Extension lines . . l! 

Dimension lines . _ . 

Fig"- 54- 

distinctions of line may be obtained by using colored inks ; and much time may be 
saved by substituting for dashes, when practicable, full line in color. 



4 6 



Working Methods. 



35. Working-methods. We use this term to indicate methods which have 
sprung from the necessities or customs of engineering practice, as well as to dis- 
tinguish processes immediately effective or practical from those which are educa- 
tional on general lines. 

For convenience, merely, we separate the process of drawing into two general 
stages, a. first, or constructive, and a second, or final, stage. Furthermore, we may 
assign to each general stage any number of special or local stages. Thus, for 

example, the first stage of a pencil or of an 
inked drawing is represented by the laying 
out of the drawing and all other pencil 
work which precedes the finished lining-in 
of the pencil-drawing, or the inking, letter- 
ing, etc., of the inked drawing. 

(a) Penciling ; working-methods. The 
accuracy with which a drawing is pen- 
ciled should invariably represent the re- 
quired accuracy of the final drawing ; 
that is, essentials must never be slighted 
in pencil and left for correction in the 
inking. All pencil-lines (represented by 
the narrow lines, Fig. 55) should be made 
with a 6H pencil and full, light, and very 
narrow. Line conventions (see the wide 
lines, Fig. 55), both in pencil and in ink, 
belong to the second stage of the drawing. 
In lining in finished pencil drawings, use a 
rather soft pencil (F to 3H) and emphasize 
the lines strongly. In the case of dash, 
and dash-and-dot line, do not erase between 
the dashes, as lightly drawn lines of the 
first stage become inconspicuous when the 
final lines are properly emphasized. Lines 
upon which measurements are to be laid off 
— as was the case in drawing AB, Fig. 
5 5 — , and lines required to be intersected 
by subsequent ones, as EG, EF, must be drawn long enough to insure the laying 
off of the measurement, or the intersection, without patching out the line. An 




Fig. 5 5- 



Working Methods. 



47 



objection to dash-lines, in the first stage of the drawing, is suggested by Fig. 56, 

in which A, B, and C, required inter- 



\\ 



\ 



sections, are merely open spaces be- 
tween the dashes. 
s'' \ (o) Inking; working -methods. 

^y \ To save time and also to minimize the 

s' \ chance of smearing wet ink, similar 

s \ operations should be grouped. To 

S* ^— illustrate, the local stages observed in 

pjo- eg inking the drawing reproduced in A, 

Fig. 5 7, are pointed out in Figs. B, C, 
D, and E. Beginning at the upper left-hand corner of the drawing, and, to avoid wet 
ink, working downward and from left to right, we first ink (B, Fig. 57) all circles 
and arcs of the same radius and then all remaining circles and arcs (first stage of 

A B C D E 




^ 



J 



V 



J 






Fig. 57. 

the inking). Next follows the inking of the perpendiculars, as shown in C (second 
stage); then (D), of all the horizontals and other remaining lines (third stage). 
The shade lines are added (E), the measurements are put in (if), and finally the 
drawing is cross-hatched and the broken lines are indicated, as in A. 

In inking convergent lines (A, B, C, Fig. 58), to prevent them from running- 





Fig. 58. 
together near the point of convergence, let each line dry before inking another, and 



4 8 



Working Methods, — Lettering. 




carry the pen away from the point of convergence rather than towards it ; or, 
terminate the interior lines (D, E, Fig. 58) at an arc described, in pencil, from the 
point of convergence taken as center. 

Shade lines when drawn, should be added to the outer edges of straight and 
curved lines, so as not to encroach upon the surface of which the shade line is a 

boundary. In the case of circles and circular arcs the shade 
line should be placed by shifting the center. Thus, for ex- 
ample, in drawing shade lines vihk and egf, Fig. 59, the center 
was shifted from a to c, a point in dg, the distance being 
determined by eye. It will be observed that the shade lines, 
as thus drawn, do not encroach on the surface included be- 
tween the two circles. Likewise, shade line stuv, added to 
the outer edge of st, does not encroach upon the surface, qrst, 
of the ring. 

36. Lettering. In connection with the study of me- 
chanical drawing it is important to have extended practice in 
lettering and dimensioning (Art. 37). 

(a) Letter styles and sizes. Figs. 60-67 (Plate 4) show letters and numerals 
— in two styles, sizes, and widths of line — to be used in rendering data and di- 
mensions on the practice drawings. In lettering titles, the same styles should be 
used, but the letters should be larger. There should be lettered on the margin of 
all practice drawings the title, — as, for example, "Finished Plate 15," "Study 
Plate 6," — the student's name, and the date when a drawing is completed. 
Heights for this lettering are given for two sizes of border-line (Fig 70). 

V&FX.ATE 5 

I l< /" 1 



Fig. 59. 



-/2"x /8" border-line- 



U" 



"^PLATE 5._ 



Q" x /2" border-line 



V— . 



DATE"" - Z^MJINAM Ei 



qat_e:: ".""iImkame 

Fig. 70. 
In general, drawings strong or heavy in appearance require a correspondingly 



Plate 4. 



ABCDEFGHIJKLMNOPQRSTUVWXYZ 
12345678908c abcdefghijklmnopqrstuvwxyz 



Fig. 60. 



ABCDEFGH/JKLMNOPQHSTUVWXrZ 
/234567890& aabcdefgh//'k/mnopqnstuvwxyz 



Fier. 61. 



ABCDEFGHIJKLMNOPQRSTUVWXYZ 
12345678908c abcdefghijklmnopqrsLuvwxyz 

Fig. 62. 

ABCDEFGH/JKLMNOPQBSTUVIA/XYZ 

/Z3-4-3G73QO& aobcc/efgh/jk/mnopqrstuviA/xyz 

Fig. 63. 

ABCDEFGHIJKLMNOPQRSTUVWXYZ 
12345678908c abcdefghijklmnopqrstuvwxyz 

Fig. 64. 

ABCDEFGH/JKLMNOPQRSTUVWXYZ 
/2345678QO& aobccfefgh//'k/mnopgrstuvwxyz 

Fig. 65. 

ABCDEFGHIJKLMNOPQRSTUVWXYZ 
12345678908c abcdefghijklmnopqrstuvwxyz 

Fig. 66. 

ABCDEFGHUKLMNORQHSTUVWXrZ 

/P34567890& aobcdefgh/jk/mnopqrstuvwxyz 

Fig. 67. 

Fig. 68. 

^e ^16 b 5a ^<9 ^/<r <%e -< >-r<—<2 — Ss— *i 

Fig. 69. 
(49) 



Lettering. 



5i 



heavy letter. If the general effect of a drawing is light — as in a geometrical con- 
struction — a light letter should be used (compare Figs. 60 and 62). In render- 
ing dimensions and data having a line width corresponding to that in Fig. 63, the 
pen recommended is a Gillott's No. 303. In the case of working-drawings, letters 
and figures having a considerable width of line are demanded, as heavy as those in 
Fig. 60 or heavier, and the pen should be a ruling-pen ground for lettering (e, Art. 
37), a coarse writing-pen, a ball-point, or a turned-point pen, the choice being 
a matter of personal preference. 

(i?) Letter rendering; working-methods. From the standpoint of common 
office practice, all reference letters and single dimensions should be rendered with 
strokes of the pen, as indicated in Fig. 68, and without the aid of guide-lines. 
The student should letter the practice drawings according to this method ; and, to 
acquire proficiency, he should practice daily, according to Fig. 68, the letters and 
numerals given in Figs. 60-67, untu ne can make them with a reasonable degree of 
speed and uniformity. In the case of lines of letters or numerals, one guide- 
or base-line may be drawn. It will be seen that (Fig. 69) the center-line of a 
fraction, whether vertical or inclined, should bisect the numerator and the 
denominator. 

(e) Letter rendering with the ruling-pen. An example of rapid-stroke let- 
tering executed with the ruling-pen is given in Fig. 71. The cut is half the size 




0.4- 



0.35 



LSioTnsirn 



for TubsM^crfvz^ 



By : 4azft»;and bWiJ I iarns • rbrmula- 

v=cR^ 6S s % *(o.ooir°:?fei_ 




IpiVhert C=I00. V=55.0 D^S 

' H f =0.000_598 ^nt 



Of 



_JG~:Co«-ff rciorrhoP- roughness- 
V= VelocHy in -frparscc- H*. = Fricrtion- loss 

R=-Hydraulio-rn«s»rnfaolius- in- -fl-p-fr-jBrtpe 

S= STop«.=nsrtio-fti)l-1blenff1h- L_ t LcaTJert+V ' 

V'P=Di3Tri«-terp)pe,---fit«£ ■ ,~ '-. ■ pippin- 




0.1 



to K co a 
DiagTsim-H' 



457 
S&2 



big. 71. 
of the original, which was taken at random from a large number of office drawings 
equally well lettered, and in a like manner. 



52 



Lettering, — Dimensioning. 



The special advantage in using the ruling-pen is the increase obtainable in 
the size of the letter and in its line width. As to the pen, an inexpensive or 
an old one is sufficiently good for the purpose. To form the point, hold the pen 
perpendicular to the oil-stone, and grind until the point is very blunt. Next 
hold the pen as in Fig. 51, and grind until the general figure of the two blades, 
taken together, is approximately conical, except at the point, which should remain 
blunt. Finally, starting with the pen held perpendicular to the stone, carry its 
point in a circular path, meanwhile constantly changing the general direction of the 
pen from the perpendicular, to take all possible angles between the perpendicular 
and 45 with the stone — a movement which changes the roughly blunted point 
to one having a spherical shape. 

To letter with the pen, hold it at an angle between 45 ° and 60 ° with the 
paper, with the thumb resting on the head of the regulating screw, which should 
be horizontal. It is best to fill the pen with the common writing-pen, or a quill, as 
wiping is likely to draw too much ink from between the blades. 

37. Dimensioning. This term signifies the giving of measurements on 
drawings (Fig. 72), and includes the rendering of the numerals, their arrangement 





Fig. 72. 
on the drawing, and the selection of their size and style. A dimension line is one 



Dimensioning, — Study Plate i, 



53 



drawn from a measurement to the arrow-heads indicating the points of measure- 
ment. Extension lines — see the vertical lines composed of short dashes, Fig. 72 
— are used in case of interference or confusion, to carry points of measurement 
to another part of the drawing. The sign ' means feet, and the sign " means 
inches: thus io 1 — 6i" is read ten feet, six and one-half inches. The quantities 
feet and inches should always be separated by a dash (Fig. 69, Plate 4). Line 
widths and lengths of dashes for both dimension and extension lines are given in 
Fig. 54. Average-sized numerals, to be used in dimensioning the practice draw- 
ings, together with the proper form of arrow-heads, are given in Fig. 69, Plate 4. 



STUDY PLATE 1. 

For practice in the accurate use of the T-square, triangles, scale, pricker, and ruling-pen. 

Size of the plate, when trimmed, to be 14 11 x 20", with a i" margin. Use 
Whatman's hot-pressed paper. 

Penciling. Sharpen the 6H pencil to a ruling-point (a, Art. 23). Make all 
the lines full, very narrow and light, but distinct. Lay out a 12" x 18" border-line ; 
work from the upper and left-hand edges of the paper (d, Art. 24). For location 
and other measurements, see Plate 5. 

(a) Locate, and rule with the T-square, the horizontal lines, Fig. A, Plate 5 ; 
start each of these lines at a vertical line (KL, Fig. 73) drawn i£" from the left- 
hand side of the border-line. Using the scale and the pricker, lay off accurately 
(b, Art. 29), as many times as the length of each line will permit, the following 



measurements : on line A, 



on B - 7 - 11 ■ f -j-\^ ■ n an . p 



an 



F, 



3 11 



Ht_ I I 



On line H lay off in succession -g 



9_H 15 11 
2 ) 3 2 > 1 (T ) X'S 



1 311 2 111 nnfl 9 11 T,, 

» S ) 35 > anCl "Iff • in 



K* 



7" 



32 






32 K 



B 



3"_ 
4 



laying off the measurements on each line, do not move the scale. Test. Using T- 
square and triangle, drop a perpendicular, as ac, Fig. 73, from each point of meas- 
urement in line A. See whether each 
perpendicular passes through the imagi- 
nary center of each alternate division, in 
line B, as point b ; also, whether each per- 
pendicular from line A passes through 
every fourth point, as c, in line C. Con- 
tinue the test as shown by Fig. 73. 

(b) With the triangle placed against 
the T-square, rule the perpendiculars, Fig. 
B, Plate 5. 

(c) Draw the rectangles, Fig. C, to 
the scales indicated. 

Fig. 73. (d) Locate point A in Figs. D, E, 

II, and y, and point />' in Figs. F and G. 
Through these points draw, indefinite in length, the vertical and horizontal lines. 






I6£_ 



rs 



Pigp. 

32 



9" 
16 



3" 



32 



9" 
16 



54 Study Plate i. 

Rule the equally spaced parallel lines, making the angles of 45 °, 6o°, and 30 with 
the horizontal. In each case the spaces must be laid off at right angles to the 
required lines (see Fig. 27). 

(e) Draw the line AB, Fig. K, and locate point C. Using two triangles, draw 
the equally spaced lines parallel to AB {d, Art. 26). Rule the lines perpendicular 
to AB (see B, Fig. 30) and lay off their length. Rule the lines drawn from points 
E and F (see Fig. 30) ; terminate the lines by circular arcs, as shown in Fig. K. 

(/) Using the T-square and 30°-6o° triangle, draw Pigs. L and M. Test. In 
Fig. L, with the 30°-6o° triangle placed against the T-square, bisect the angles, 
and see if the bisectors intersect in the same point. In Fig. M, with the 45 ° 
triangle placed against the T-square, draw the diagonals of the square, upward from 
the ends of the base, and see if each passes accurately through an upper corner of 
the square. 

(g) Begin Figs. iVand O by repeating Figs. L and M. Find, by scale meas- 
urement, the middle point of each side of the triangle (Fig. N) and draw CD, BD, 
and AD, respectively perpendicular to a side of the triangle. Lay off on each 
perpendicular the measurements given on BD. Through these points, using T- 
square and triangle, draw the sides of the interior triangles. Test. Produce CD, 
BD, and AD, and see if the alignments of the corners of the triangles are accurate. 

Find by scale measurement the centers C and B of two sides of the square 
(Fig. O). Draw the diameters, CD and AB, of the square. On each semi-diameter 
lay off the measurements given at C. Through these points draw the sides of the 
interior squares. Test. Draw the diagonals of the outer square and see if they 
pass through the center of the square, as located by the diameters, and also if they 
pass through the corners of the inner squares. 

(/i) Draw the hexagon, P"ig. P, according to the given angles and measure- 
ment. Test. Connect the opposite angles of the hexagon and see if the diagonals 
thus obtained intersect in the same point. 

(z) Draw AB, Fig. Q. Using T-square and triangle, complete the hexagon 
without further scale measurement. Test. Measure with the scale each side of 
the hexagon, and see if all have the same length. 

(J) Having finished the penciling, the drawing is now to be used as the pre- 
liminary for a tracing, after which it is to be finished in ink. In general, if a drawing 
is made for a tracing, all lettering and dimensions should be suggested before the 
tracing is begun ; but, when a drawing is required to be finished in ink, the letter- 
ing may follow the inking. In the present case the lettering and dimensions 
should now be indicated in pencil, but, in view of the second use of the drawing, 
with greater accuracy and neatness than might be required for a tracing. 

Take as a guide Figs. 60 and 65, (Plate 4). Show all lettering and dimen- 
sions given on Plate 5 ; suggest also the title " Study Plate 1," your name, and the 
date, according to the measurements given in Fig. 70. In the case of single 



Study Plate i, — Study Plate 2. 55 

letters and lines of letters, rule only one guide line, above which the letters are to 
be placed. Suggest quickly and lightly the general position, quantity, form, and spac- 
ing of the letters. In the case of each dimension, rule first, if required, the exten- 
sion lines * (Art. 37); next rule the dimension line (Art. 37); then indicate the 
arrow-heads ; and last, suggest the position and size of the numerals. Work 
rapidly. 

Tracing. Work on the dull surface of the tracing-cloth. Smooth out the 
cloth as flat as possible, and fasten with four additional thumb-tacks placed midway 
between the corners. See that the ink is black. If the cloth does not take the 
ink well, use chalk (Art. 32). The lines made on the tracing-cloth should cover 
the lines in pencil accurately. 

(k) Make the lines A — H (Fig. A) full, and of the width given in A, Fig. 54. 
Indicate the scale measurements laid off on lines A — H, in the pencil-drawing, by 
ruling through the center of each point of division a very narrow line perpendicular to 
and extending about T y ' above and below the given line. Make each line in Group 
J (Fig. A) the same as the corresponding line in D — -J, Fig. 54 ; repeat for Fig. B. 
In the remaining figures make all result lines the same as the line D (Fig. 54) ; 
make incidental lines, as AB, Figs. D—J (Plate 5), like A or B (Fig. 54). The 
line of the ruled border should be slightly wider than the result lines in the drawing. 
Test. Measure with the scale the distances on lines A — H, Fig. A, as established 
in the tracing ; see if they correspond with the measurements given in Fig. jt,. 

(I) Render, directly in ink, with strokes of the pen (b, Art. 36), the lettering, 
dimensions, and signs for inches. Rule the dimension lines ; put in the extension 
lines ; and render the arrow-heads. 

(;//) Erase and redraw the lines radiating from F, Fig. K (c, Art. 33) ; use 
erasing shields (b, Art. 33) to protect the lettering, erased portions of which should 
be restored. 

Inking the pencil-drawing, (n) Proceed according to the instructions in k, I, 
and in ( Tracing), except as follows : Make all lines in the drawing like line A, Fig. 
54. Take for a guide in the lettering and dimensioning, Figs. 62 and 6j. The 
title, "Study Plate 1" -on account of the size of the letters — may be drawn 
(free-hand) instead of stroke-rendered. 

(0) Erase and redraw Fig. O (b, Art. 33). 

(/>) Erase pencil-lines. Do not roll the drawing. 

STUDY PLATE 2. 

For practice in the accurate use of the compass, dividers, and French curve. 

Use Whatman's hot-pressed paper. The ruled border-line is to be 12" x 18", 
with a 1" margin. Use the 6H pencil. For location and other measurements 
sec Plate 6. 

* In preliminary penciling the dimension and extension lines should be drawn in full line. 



56 Study Plate 2. 

Penciling, (a) Make all lines/)///, very narrow, and light, but distinct. De- 
scribe the circle A, Fig. A. Rule a line from the center to the circumference, 
and on this line lay off the spacing of the interior circles, the smallest of which 
is s" diameter; describe the circles, according to a, Art. 27. From the same 
center, using the lengthening bar (b, Art. 27), draw the arcs, Fig. C. 

(b) Work the following steps very accurately. Draw AB, Fig. B, and locate 
the center C, by scale measurement. Using only the T-square and the 30°-6o° 
triangle placed against the T-square, draw the hexagon, its diameters, and its diag- 
onals. Distant f" from A, locate point H, and, with C as center, describe the 
circle OHK. With f" radius, centers on circle OHK, describe the circles tangent 
to the sides of the hexagon. Establish the points of tangency, as P, Q, and R, by 
drawing, with C as center, the circle through point P, which is the intersection of 
HK and CT. Tests. With C as center, radius CA, describe a circle ; see if the 
imaginary center lines of the three tangent lines at A, G, E, B, F, and D, inter- 
sect in a point (Fig. 42). With f" radius, C as center, draw a circle; see if, in 
its intersection with each diameter of the hexagon, it is tangent to each of the six 
equal circles. If the results in the foregoing constructions are found to be inaccu- 
rate, all lines should be erased, the line AB moved k" to the left, and the con- 
struction repeated. 

(c) From line LH, indefinite in length, draw lines A — F, Fig. D. With the 
hair-spring dividers, and according to a and b, Art. 30, space the lines into equal 
parts, as follows: D, 17 parts; B, 13; C, n. With the bow-spacers divide 
equally as follows : A into 1 7 parts ; E, 13; F, n. Test. Locate point L by 
producing line yAT. Draw through point L a straight line from each point of di- 
vision on line D. See if the line from each of these points passes through the 
corresponding point of division in line A. Test in like manner the points of 
division in lines B and E and in lines C and F. 

(d) Draw, Fig. E, the circles, circular arcs, and line EM. With the hair-spring 
dividers, and starting at line EM, space the circles A and B each into 19 equal 
parts. With the bow-spacers, starting at line EM, divide circles Cand D each into 
19 equal parts. Test. Draw very accurately from center E to each point of 
division in circle A ; see if each line passes through the centers of the correspond- 
ing divisions in circles B, C, and D. 

Draw EG through point 14, Fig. E. With the hair-spring dividers space 
equally arc //A r into 5 parts ; JO and LQ each into 9 ; KP and MG each into 7 
parts. Tests. Draw from center E, through points 15, 16, 17, and 18, circle A; 
see if these lines produced pass through the centers of the points of division in arc 
HN. From center E draw through the points of division in JO, and produce the 
lines to intersect LQ ; see if the lines pass through the centers of the points of 
division in LQ. From center E draw through the points of division in MG ; see 
if the lines pass through the centers of the points of division in KP. 

(e) The curves A — J, Fig. F, are to be located by pricking through the curves 



Study Plate 2. 57 

given in Plate 7, and the points thus obtained are to be connected free-hand (a, 
Art. 28). To prick off the points, proceed as follows : Draw a short perpendicular 
across the lower horizontal line of the ruled border-line, 6" from its right-hand end. 
Cut holes through Plate 7, one hole at each end of line AB, and one on ab. Now 
tack this plate over the drawing, taking care not to press the thumb-tacks through 
the drawing or its margin ; place AB over the ruled border-line, and ab on the per- 
pendicular located 6 11 from the corner of the border-line. The location and the 
number of the points to be pricked through must be determined by judgment aided 
by the following suggestions. In the sharp curves at the ends of curve F (Plate 
6) take the points from 5 V to tV apart, and, for the flattest portions of the same 
curve, from ]" to |" apart. The points at the ends of curve A (Plate 6) should 
be from J" to ^V" apart. In the ellipses the ends of both axes should be pricked 
through and the axes ruled before sketching in the curve. 

(/") Indicate the lettering and dimensions given in Plate 6, and also the title 
" Study Plate 2," your name, and the date (see/, Study Plate 1). Note that, as in 
Study Plate 1, the present drawing is to be traced, after which it is to be regarded 
as the first stage of a finished drawing in ink. 

Tracing, {g) Trace the drawing accurately. Ink in the circles A — F, Fig. 
A, to correspond to the lines A — F, Fig. 54. Repeat for circles G — M, Fig. A. 
Make the two remaining circles like line A, Fig. 54. Ink in the arcs A — F, Fig. 
C, to correspond to the lines A. — F, Fig. 54. In the remaining figures ink in the 
result lines, like line D, Fig. 54, and make the incidental lines, like line A, Fig. 
54. Omit the lines used in the tests. Indicate the points of division obtained in 
the spacing by a short line perpendicular to the divided line, whether circular or 
straight, as directed in k, Study Plate 1. The line of the ruled border should be 
slightly wider than the result lines in the drawing. 

(//) Render the lettering, dimensions, dimension and extension lines, signs, 
and arrow-heads according to j, Study Plate 1 . 

(/) Erase and redraw ellipse D, Fig F (c, Art. 33). 

Inking the pencil-drawing. (J) Proceed according to g (Tracing, Study Plate 
2), except as follows : In Figs. B, D, E, and F, make all the lines of the width A, 
Fig. 54. In inking the curves, A — -J, proceed strictly according to the instructions 
given in a, Art. 28 ; if strictly accurate results cannot be obtained, with the French 
curves available, templates should be made (/;, Art. 28). Ink the axes of the 
ellipses, and all lines used in the tests, full, very narrow, and in red. Take for 
a guide in the lettering and dimensions Figs. 62 and 67. The title " Study Plate 
2 " should be drawn instead of stroke-rendered. 

(k) Erase and redraw F, Fig. F (b, Art. 33). 

(/) Erase pencil-lines. Do not roll the drawing. 



58 Geometrical Construction. 

CHAPTER III. 

GEOMETRICAL CONSTRUCTION. 

The following problems are given for further practice in precise rendering and 
for their application in practical drawing. As to application, it should be under- 
stood that the use of such problems is not necessarily confined to the drawing- 
room or to drawings of the usual sizes. The mechanic, for example, may need to 
work out a geometrical construction to the actual size of the work in hand, on wood, 
metal, or on the floor of the shop, and in large work substituting chalk-line for 
straight-edge, and striking the arcs with a piece of chalk held at the end of a string 
or strip of wood swung from a nail as a center. Likewise, we may see the land- 
scape gardener laying out a problem directly on the ground, stretching the tape 
for a straight-edge and describing arcs with aid of tape and measuring pins. 

In the precise rendering of problems the student should continue to hold him- 
self to the strict observance of details concerning the condition of his instru- 
ments and their handling. In penciling, all lines should be drawn with a 6H pencil, 
full, and as narrow as possible. Lines required to meet in a given point, as at the 
corners of a polygon, and lines drawn to a point determined by intersecting lines, 
should not stop at the point but should be drawn through it. When the extremity 
of a line is used in measuring, as a center for the compass, or otherwise, it should 
be definitely located, either with the pricker or by a shortruled line drawn at right 
angles to the given line. Intersecting arcs, for appearance, should be made of 
equal length, and for accuracy should be placed as nearly at right angles as possible. 
For greater accuracy, every point required to be used as a center for the com- 
pass should be noted with the pricker before placing the needle point of the com- 
pass ; this is especially necessary if the paper has a grained surface, since the in- 
equalities of the surface are more likely to deflect, unobserved, the needle point of 
the compass than that of the pricker. In inking, unless otherwise directed, all 
lines should be made full, of the same width, and as narrow as possible without sac- 
rificing quality of line. Given lines may be drawn in blue, construction lines in red, 
and result lines in black. 







Problem 1. — 71? bisect a straight line, as AB, or a 
circular arc, as AE' B. With any appropriate radius, A 
and B as centers, describe arcs intersecting in C and D. 
Draw CD. E and E' are the required middle points. 






1/5 

ft 





2 







CD 



CO 






LIBRARY OF CONGRESS 



029 985 414 



